1. Field of the Invention
The present invention relates to films useful in or for forming microelectronic devices and to methods of manufacturing the same, and more particularly, to multi-layered dielectric films which can improve the performance characteristics of microelectronic devices which incorporate such films, and to methods of manufacturing the same.
2. Description of the Related Art
As semiconductor devices have become increasingly highly integrated, the area of a unit cell of such semiconductor devices has become smaller. Accordingly, cell capacitance has been reduced. A reduction in the cell capacitance, however, adversely affects an integration level, which will be described by reference to examples of various types of electronic devices.
In connection with a high voltage (e.g., 15 V or greater) device, such as a liquid crystal display (LCD) drive IC (LDI), reducing cell capacitance may increase a boosting frequency resulting in a large amount of power dissipation. In addition, there may be a limitation in reducing the entire chip size. In connection with a memory device, the reading capability of a cell is degraded by reducing cell capacitance, and a soft error rate increases. In addition, low voltage driving of such a device is difficult to achieve, and overly excessive power dissipation may be caused during the operation of the device. As such, in order to manufacture a high-voltage semiconductor device or a memory device with an ultrahigh integration level but without these capacitance-related drawbacks, it is necessary to develop a method of increasing cell capacitance, that is, capacitance per unit area.
In general, the dielectric property of the dielectric layer used in a capacitor can be evaluated by an equivalent oxide film thickness (known as a Toxeq value) and by a leakage current density. The equivalent oxide film thickness (Toxeq) is a value obtained by converting a thickness level of a dielectric film formed of a dielectric material other than a silicon oxide into an equivalent thickness level of a dielectric film made of a silicon oxide. As the Toxeq value is reduced, cell capacitance per unit area increases.
The leakage current density is also associated with the electrical characteristics of a capacitor and with power dissipation. That is, the smaller the leakage current density of a semiconductor device, the better the electrical characteristics of the device.
In order to increase the cell capacitance of a semiconductor device, a combination of a silicon oxide (SiO2) layer (hereinafter referred to as the ‘O’ layer) and a silicon nitride layer (Si3N4) (hereinafter referred to as the ‘N’ layer) has been used in the prior art as a dielectric film of a capacitor. However, as shown in FIG. 1 (representing prior art technology), the dielectric constant of the silicon oxide (SiO2) film and the silicon nitride (Si3N4) film are only 5 and 10, respectively. Thus, there is a serious limitation in trying to increase capacitance using only materials having a relatively low dielectric constant.
Accordingly, research into forming a high-k dielectric film made of a material having a relatively high dielectric constant has been actively conducted in an effort to find a substitute for silicon oxide or silicon nitride films. As such, currently, considerable attention is being paid to a variety of high-k metal oxide materials as possible dielectric film materials for use in the formation of a capacitor element or layer of a semiconductor device. Identifying high-k dielectric materials which are suitable for semiconductor applications, and finding effective ways to form uniform, controlled-thickness films of such materials, however, have proven to be challenging obstacles to advancement in this field.
These and other problems with and limitations of the prior art approaches are addressed in whole or at least in part by the dielectric films and the related formation methods of this invention.